How the system works
Forward collision warning (FCW) predicts a possible conflict ahead and alerts the driver. Automatic emergency braking (AEB) can request braking when a collision becomes imminent or increase insufficient driver braking. Pedestrian AEB is a separately assessed capability in many schemes; detecting a car in front does not prove that the same system detects every pedestrian or cyclist. NHTSA's FMVSS 127 actions address vehicle and pedestrian braking, but they do not retroactively establish performance for all existing 2020–2026 used cars.
What it can and cannot do
Sensor data may come from a camera, radar or a combination, processed to estimate closing speed and classify targets. AEB has to balance late action against unnecessary interventions. It may not react as expected to blocked pedestrians, sharp bends, glare, rain, snow, dirty sensors or unusual object geometry. Speed and target categories can have explicit design limits. Even when a feature operates correctly, braking distance still depends on tyres and road grip.
What changes between vehicles
An AEB logo is not a specification. Some variants emphasize city-speed vehicle collisions, others extend detection to more scenarios, and test procedures evolve. A manufacturer may change the camera, radar, software or standard equipment across trims and countries. To evaluate claims, compare the exact vehicle's manual and dated independent protocol results. Do not assume a favorable test grade from a different model year or region follows the same badge.
Buying and ownership implications
For a used car, check whether front-end bodywork, radar mounting or windscreen replacement required sensor calibration. IIHS has documented that safety sensor repairs are more complex than visible panels alone suggest. Ask for proof of calibration if required by the OEM, investigate persistent warnings and never test automatic emergency braking by staging a collision or having a person stand in front of a moving car.
Regional and model-year caveats
In the global catalogue, describe confirmed detection categories and operating limits for each model-year-market variant only when supported by OEM documentation. Legal obligations should be dated and tied to a jurisdiction; proposed changes do not equal active rules. AEB is an additional chance to avoid or mitigate harm, not a substitute for safe following distance, speed management or attention.